8.21. Reading Environment Variables

8.21.1. Problem

8.21.2. Solution

8.21.3. Discussion

Environment variables are named values associated with a process.
For instance, in Unix, you can check
the value of $_ENV['HOME'] to find the home
directory of a user:

print $_ENV['HOME']; // user's home directory
/home/adam

Early versions of PHP automatically created PHP variables for all
environment variables by default. As of 4.1.0,
php.ini-recommended disables this because of
speed considerations; however php.ini-dist
continues to enable environment variable loading for backward
compatibility.

The $_ENV
array is created only if the value of the
variables_order configuration directive
contains E. If $_ENV
isn't available, use getenv(
) to
retrieve an environment variable:

$path = getenv('PATH');

The getenv( ) function isn't
available if you're running PHP as an ISAPI module.